A type of display board is currently available for providing an interchangeable background, covered by a transparent acrylic sheet. In one style of this type of board, the acrylic sheet is mounted to a hinge at its top and retained by magnets at its bottom. The magnets are attracted to a steel sheet that is about 0.32 mm thick, to which the acrylic sheet hinge is also mounted. To provide or change the semi-permanent display, the cover is opened and printed media, in the form of printed coated paper or polymeric material is placed over the steel sheet, and the Plexiglass cover is closed. This provides the user with a board having a printed background, but that he can write on with a marker, and later erase. As an example, a basketball coach may want a board having a basketball court scheme as a background, upon which he can draw basketball plays. Using the board described above he could order a basketball court scheme on cardboard or polymeric media and place it between the metal backing and the acrylic sheet cover, close the cover, and then mark the plays on the acrylic sheet. During football season the board could be provided with a football scheme background and provided to the football coach, who could draw football plays on it. In a medical environment, a board assembly in an ear, nose and throat specialist's office could be used to show a background media of the human throat, permitting the physician to mark on the clear plastic over this media, to illustrate a throat procedure. The same style of board could be used in a cardiologist's office with media showing the interior of the human heart, to permit the cardiologist to explain a cardiac procedure to a patient.
Unfortunately, many of the available boards of this nature are problematic. First, many include a wood backing to the steel sheet, thereby making the board quite heavy. Moreover, wood forming a portion of the board causes the board's use to be prohibited in many portions of a hospital, including patient rooms. Any porous material, such as wood, provides places for microbes to dwell, where it is difficult for sanitizing agents to reach. Also, as the principal structure of the board is wood, the steel sheet tends to be quite thin, on the order of a third of a millimeter. Also, a frame is generally used to hide the layered construction from users, and to forestall potential delamination. This adds to the weight of the board and provides additional covered areas for harmful microbes to live.
Further, in some hospital rooms a “terminal cleaning” is performed when a patient with a highly infectious condition is discharged. In this procedure, everything in the room is hosed down with bleach. Boards that include wood or a laminated panel as part of their construction tend to be damaged by being exposed to large amounts of bleach water. In like manner, boards containing wood may also be more vulnerable to becoming warped if left outside in the rain, as an advertising sandwich board might be left.
Finally, the differing coefficient of thermal expansion of the wood versus the steel sheet tends to cause warping in the steel sheet. It appears that this has necessitated the use of a thicker acrylic sheet than would otherwise be necessary, so that the weight of the acrylic sheet can hold the media in place, even against an uneven backing surface.